High-frequency tube structure



Jan. 21, 1947. A. E. HARRISON ETAL 2,414,785

HIGH FREQUENCY TUBE STRUCTURE IIIIII IIIIIIIIIIII F 6 7 INVENTORS:

THEIR ATTORNEY Jan. 2l, 1947. A. E. l-umRlsoNr ETAL 2,414,785

HIGH FREQUENCY TUBE STRUCTURE Filed Ja n. 29. 1942 7 Sheets-Sheet 2 FIG. 8

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A.E. HARRISON S.E VARIAN INVENTORSI TH E IR ATTORNEY 7 Sheets-Sheet 3 wn o e mm n Il l1 i MM N G HV R ll. 5 4 3 o F m 7 0 7 l/ 8 .M o EE W //l |l H.. n m AS (JA l Mlle I. \\V s I5 l M e l a m l l i l H n.- M l m E fr 8 5 MIK 2 V 8 G l lt. r .l m x l 7 Il llll. I .l F 9 m -H 2 .e 9. .fl 3 8 7 Jan. 21, 1947. A. E. HARRISON ETAL HIGH FREQUENCY TUBE STRUCTURE Filed Jan. 29, 1942 y .n 6I s u n n im D. C n 2 M m m 2 U A l T y 2. m 3 M 2 v u Ill Pq u. T m n n A o... Tm n .u .f v. un R InlU N .II w v f Illlll Irlll liillllilflnll!! 5 q n .I n L n F F G E .l R F 11111.21, 1947. A. E. HARRIS-QN Em 2,414,785

HIGH FREQUENCY TUBE STRUCTURE Filed Jan. 29, 1942 '7 Sheets-Sheet 4 INVENTO R Si AE. HARRISON S. E VARIAN THEIR ATronNEY Jan. 2l, 1947. A. E. HARRlsoN ETAL 2,414,785

HIGH FREQUENCY TUBE STRUCTURE Filed Jan. 29, 1942 7 Sheets-Sheet 5 mvENToRs: Af. HARmsoN s.E vARlAN THEIR ATTORNEY Jan. 2l, 1947. A. E. HARRISON ETAL HIGH FREQUENCY TUBE STRUCTURE Filed Jan. 29, 1942 7 Sheets-Sheet 6 FIG. 22 v INVENTORS:

THEIR ATTORNEY Jan. 2l, 1947. A. E. HARRISON Erm. 2,414,785

HIGH FREQUENCY TUBE STRUCTURE Filed Jan. 2s, 1942 v sheets-sheet 7 FIG. 25

A. E. HARRISON 8.5 VARIAN INVENTORSZ THEIR ATTORNEY wavelengths on the Patented Jan. 21, 1947 2,414,785 HIGH-FREQUENCY TUBE STRUCTURE Arthur E. Harrison,

Oceanside, and Sigurd F.

Varian, West Hempstead, N. Y., assignors to Sperry N. Y., a

Gyroscope Company, corporation of New York Inc., Brooklyn,

Application January 29, 1942, Serial No. 428,682

(Cl. Z50-27.5)

25 claims. 1

This invention relates, generally, to ultra high frequency vacuum tube structure; and, more specically to ultra high frequency devices of the electron beam type such as disclosed in Patents No. 2,245,627, entitled Stabilization of frequency, issued June 17, 1941, in the name of Russell H. Varian, No. 2,250,511, entitled Oscillator stabilization system, issued July 29, 1941, in the names of Russell H. Varian and William W. Hansen and No. 2,259,690, entitled High-frequency radio apparatus, issued October 2l, 1941, in the names of John R. Woodyard, William W. Hansen and Russell H. Varian. In the aforementioned disclosures, there is shown an ultra high frequency device consisting of an indirectly heated cathode which projects an electron beam through grids which form portions of the opposite walls of a hollow cavity conducting resonator. After the electron beam leaves the exit grid of the resonator, it is reflected back through the resonator by means of a reflector electrode operating at or very near to the potential of the cathode. If a high frequency alternating electric field exists between the resonator grids due to the Dresence of a corresponding high frequency alternat.. ing electromagnetic eld in the resonator, the electron beam suffers recurrent velocity changes by the action of said alternating electric field during its initial passage through the resonator. As the electron beam passes through the exit grid of the resonator and onward, the effect is to commence to produce recurrent grouping of the electron beam. The spacing between the resonator exit grid and the reflector electrode, and the voltage on said electrode, are so arranged that the electrons are reflected back into the resonator at a time when the recurrent velocity changes have resulted in recurrent grouping of the electron beam and at a time such that these electron groups return energy to the alternating electric eld appearing between the resonator grids, thus maintaining the oscillating electromagnetic field inside of the resonator. Direct current energy is thus introduced into the device by means of the electron beam, and may be removed as ultra high frequency energy from the hollow resonator by means of coupling loops and associated concentric line elements, as more Ifully described in the aforementioned patents.

One object of the present invention is the provision of improved tuning means for high frequency tube structures of the type employing a single resonator such as disclosed in the abovementioned patents, suitable for operating at order of ten centimeters or less.v

Another object of the present invention is to provide improved cavity resonator electron-discharge tube structure of the reflex type suitable for operation at wavelengths on the order of 10 centimeters or less.

A further object of the present invention is to provide improved combined mounting and tuning means for high frequency tube structures containing cavity resonators.

Other objeots and advantages of this invention will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings,

Fig. 1 is an elevational and partially cross-sectional view of a preferred form of the vacuum tube and tuner mechanism of the present invention.

Fig. 2 is a plan View of Fig. 1.

Fig. 3 is a perspective view of a detail of Fig. 1.

Fig. 4 is a cross-sectional view of an element of Fig. 1.

Fig. 5 is a fragmentary plan view of a detail of Fig. 1.

Fig. 6 is a cross-sectional elevation view of an alternate form of a portion of Fig. 1.

Fig. 7 is an elevational view of a grid structure.

Fig. 8 is a cross-sectional elevational view,

with parts omitted, of an alternate form of the structure shown in Fig. 1, together with a schematic wiring diagram.

Fig. 9 is a fragmentary cross-sectional View of a detail of Fig. 8.

Fig. 10 is a similar view of an alternate form of the structure of Fig. 9.

Fig. 11 is a perspective view of a modification of the structure shown in Fig. 9.

Fig. l2 is a partially cross-sectional elevational view of an alternate of the Figs. 1 and 8.

Fig. 13 is a fragmentary perspective view of a detail of Fig. 12.

Fig. 14 is a fragmentary cross-sectional elevational view of an alternate form of the cathode structure shown in Fig. 12.

Fig. 15 is an explanatory graph.

Fig. 16 is a cross-sectional plan view of a resonator similar to that of Fig. 8.

Fig. 17 is a fragmentary cross-sectional elevation view of an alternate form of a portion of Fig. 12.

Fig. 18 is a cross-sectional plan view taken along the line I8-I8 of Fig. 17.

Fig. 19 is a partial cross-sectional elevational view of an alternate form of Figs. 1, 8, and 12.

structures shown in Fig. 20 is a cross-sectional elevation view of a modification of a detail of Fig. 19.

Fig. 21 is a partial cross-sectional elevationA view of an alternate form of the structure shown in Figs. 1, 8, 12 and 19.

Fig. 22 is an elevation View in cross-section of a modied form of the device shown in Fig. 1.

Fig. 23 is a cross-sectional plan view taken along the line 23-23 of Fig. 22.

Fig. 24 is a fragmentary partial cross-sectional elevation view of an alternate for'm of a portion of the structure of Fig. 19.

Fig. 25 is a fragmentary cross-sectional elevation view of an alternate form of the structure of Fig. 24,

Similar characters of reference are used in all of the above gures to indicate corresponding parts.

In Fig. 1 there is shown a single resonator electron beam velocity-modulating tube structure of the type disclosed in the aforementioned patents, together with a novel type of frequency-adjusting mechanism. The cathode structure consists of emitter surface I, which may be of the oxidecoated type, heated by resistance heater 2, emitdrical neck portion 1 in which grid 5 is mounted and which serves to provide a field-free space in which the electron beam travels toward and through entrance grid 8 of a hollow conducting resonator 9. Resonator 9, as shown, as a reentrant portion I0, a flexible end wall I I, an outer cylindrical wall I2, and rigid flat end wall I3 opposite to wall II. apertured and carries a grid structure I4 concentric with and clos'e to grid 8. Grids 5 and I4 may, as shown in Fig. 5, consist of an annular member provided with alternate long and short radial conducting bars I5 and I6 and inserted in rings I1, which in turn are inserted in plate 5 and end wall I3. Grid 8 may be made of strip material put preferably into cruciform shape and secured in a ring 8' as illustrated in Fig. 7. The elements of grids 5, 8, and I4 may be made of zirconium or other metals which emit relatively few secondary electrons. Spaced concentric to grid I4 and close behind it is reector electrode I8 z which may be dish-shaped as shown. Reflector I8 is supported by conductor I9 which passes through glass end bell 20, which is in turn supported by end wall I3 of resonator 9 in the conventional manner.

In operation, the electron beam emitted from cathode I is projected through accelerating and smoothing grid 5 and through entrance grid 8 into resonator 9. In this resonator the beam suers recurrent velocity changes or is velocitymodulated by means of an oscillating electric field existing between grids 8 and I4. 'Ihe beam travels out through exit grid I4 and is reected back through grid I4 by a voltage applied to reector I8 very near that of the cathode I voltage, the reentry of the beam into resonator 9 taking place after recurrent bunching or density. modulation of the beam has taken place, said grouped electron beam then giving up energy to A John R. Woodyard and is described and claimed ter I' being coaxial with and surrounded by fo- End wall I3 of resonator 9 is I in his copending application entitled Highfrequency terminal filed on December 14, 1946. In this figure, a tube 23 which may be of Kovar or other metal readily sealable to glass, forms the outer conductor of the concentric line post and is inserted into an aperture in wall I3 of resonator 9. The inner rod 24, concentric to tube 23, serves as the inner conductor, may be of tungsten, and is positioned by glass seal 25. Inner end 26 of rod 24 supports one end of coupling loop 21, the other end being welded to the inner end of tube 23.

The outer end of inner conductor 24 is conical to facilitate fitting of the inner conductor of the concentric line to be thereto attached. Slightly above the outer surface of glass seal 25, rod 24 has a constricted section 28. It is found that without the small diameter section 28, if the end of rod 24 is accidentally hit, glass seal 25 would break near rod 24; but that if the constricted section 28 is provided, section 28 merely bends if accidentally hit, and the seal 25 is not broken.

Concentric line terminal posts 2|, 22 may be placed so that they project radially from cylindrical wall I2, as shown in the aforementioned Patent No. 2,245,627. A structure such as shown in Fig. 6 may also. be used, in which a coaxial line terminal post 5B of conventional type or similar to that shown in Fig. 4 is adjustably positioned in a reentrant tube 51 of low loss glass, tube 51 being sealed to a concentric metal tube 55 inserted in wall I2 to provide continuity of the vacuum envelope. It is evident to one skilled in the art that rotation of the post 56 and hence of the coupling loop 59 out of the plane shown in Fig. 6 decreases the coupling between resonator 9 and coaxial line post 56, and this is also true if post 56 is moved outwardly.

End plate B and end wall I3 in Fig. 1 are provided with flange extensions 3B and 29, respectively, which flange extensions are perpendicular to the axis of the tube. The entire structure may be supported as from a panel 32 by means of a forked bracket 3l which is clamped to flange 30 by screws 33, as is seen in Fig. 1. Bracket 3| has an inner threaded cylindrical portion 34 which is adapted to fit through a round hole in panel 32. The external diameter of cylindrical portion 34 is threaded to receive nut 35 which clamps bracket 3l to panel 32, by forcing panel 32 against shoulder 36 of bracket 3i.

Flange 29 is shown provided with three screws 31, 31', 31" which may be spaced 120 apart near the periphery of said flange, their slotted ends facing away from ange 30. Screws 31' and 31" are provided on their inner ends with socket joints 38 for receiving the spherical ends of cylindrical struts 39, which struts have hemispherical ends 40 bearing in sockets in ange 30. Screw 31 is likewise provided on its inner end with a socket for linking said screw with strut 4I that is similar to struts 39. Strut 4I has a hemispherical end 4I( thrusting against a conical seat 45 provided in a lever 43. Lever 43, as seen in Fig. 3, consists of transverse portion 46 and a portion 41 extending at approximately right angles thereto, the lever 43 being braced by a web portion 44. A pivotal support for the lever is provided by two studs48 and 49 supported in flange member 30. The upper end of stud 48 ts into conical hole 50 in the bottom surface of lever portion 46, while the upper end of stud 49 fits into of V-shaped cross-section, said slot extending at right angles to the length of lever 43, and in line with hole 50.

Struts 39 and strut 4| are forced to bear with a, proper force against flange 30 by three springs 42, 42', 42" which are under tension between flanges 29 and 30, which may be spaced 120 apart near the peripheries of said flanges, and which may be 60 from the screws 31, 31', 31". It is thus seen that a kinematic lever arrangement has been provided which is strained and has as its degree of freedom the ability to be rotated about the pivotal supports 48, 49, in the plane of the drawings of Fig. 1, thus imparting motion to stud 4| and flange 29 and flexing wall II, for varying the distance between grids B and I4, thereby changing the natural frequency of the hollow resonator 9.

Actual movement of the lever portion 41 is produced by rotation of a screw 52 by a knob 53. Screw 52 has a hemispherical face 54 which bears against the outer face of lever portion 41. Relative placement of pivots 48, 49 and stud 4I and the pitch of screw 52 determine the fineness of the resultant frequency adjustment. Rough adjustment may be provided by the rotation of screws 31, 31', 31".

Fig. 8 discloses a modification of the twbe structure shown in Fig. 1 having a low frequency shift with thermal changes and other advantages to be further explained. This structure is the sole invention of Sigurd F. Varian, one of the present applicants, and is described and claimed in his copending application entitled, High-frequency tube structure," led on December 14, 1946. Frequency shift may be brought about from changes in the spacing between grids 8 and I4 due to thermal expansion or contraction. As will be apparent from a study of Fig. 1, such spacing change originates largely from two sources: expansion or contraction of the cylindrical portion I0 bearing entrance grid 8 and expansion or contraction of struts 39 and 4| and associated rough tuning screws 31, 31', 31". In Fig. 8, there is shown a reflex device with low thermal coeflcient of frequency. Resonator 9, coaxial line posts 2|, 22, and reflector electrode I8 are shown substantially similar to corresponding parts in Fig. 1. Flanges 29 and 30 may be made of steel, or of other metal of low thermal conductivity, in order to avoid excessive temperature rise of the tuning mechanism thereto attached.

Reentrant portion I0 of resonator 9 continues beyond wall I and integrally flares out to flanged portion 60 parallel to flanges 29, 30, tube I0 being of one of the well known high nickel content alloys suitable for butt sealing to certain glasses and having very low thermal coefficients of expansion and preferably having all of its surfaces inside of resonator 9 plated with copper or other highly conducting material. Flange 30 is attached directly to the extended portion of cylinder I0 between resonator 9 and flared portion 60. Struts 6|, corresponding to struts 39 and 4| of Fig. l, are of Invar or other material of low thermal expansion coefficient, as are also screws 31, 31', 31" engaging these studs. Other parts of Fig. 8 that are similar to corresponding parts of Fig. lsuch as tuning lever 43 and springs 42, 42',

42" are omitted in Fig. 8 for the sake of simplifying the drawing. Cathode I, which may be of any of the types to be further described, is placed inside of reentrant portion I0, thus dispensing with grid 5 of Fig. 1, and may be supported in the conventional manner by leads projecting through glass press 63 sealed to cylindrical glass vacuum envelope 62 which, in turn, is butt sealed near the periphery of flange 60.

As shown in the aforementioned Patent No. 2,250,511, the output frequency of a reflex electron beam velocity modulator may be varied by changing the voltage of the reflector plate I8 with respect to exit grid I4. As seen in Fig. 8, a voltage at or very near the cathode I voltage may be applied to reflector I8 by lead 64 tapping potentiom- 1| of transformer '68 between tap 13 of potentiometer 65 and reflector electrode I8, and supplying modulation application entitled, High-frequency modulator apparatus, led on December 14, 1946. The eiliciency of operation of such a reflex device may be enhanced somewhat by coating the front surface of reector electrode I8 with a secondary electron emissive material and moving tap 13 so that reflector I8 is at about half the accelerating voltage. 'I'hese structures are also the invention of Sigurd F. Varian, and are entrant tube portion I0 are shown in Figs. 9, 10, and 1l. Because of small spaces available in reflex oscillators and amplifiers operating in the region below ten centimeter wavelengths, more conventional types of cathode structures as shown in Fig. 1 may not be desired. A structure which produced. A frustum 15 of a right circular cone with a small diameter end of diameter substantially equal to that of conductor 14 has that small diameter end welded or otherwise secured to the upper end of conductor 14. Frustum 15 may be of nickel or other heat conducting material, and may have its large diameter surface coated with an oxide electron emission material, as at 16. The cylindrical sides of rod 14 are coated with A1203 or other material of low electrical conductivity at high temperature, as at 81, and around said coating may be wound a coil 11 of heater resistance wire. The heater assembly is surrounded by heat shield 18, which may ibe a tube of nickel, and which positions the heater assembly by means to be described. Heat shield 18 may have inserted in its lower end a double wall bottom, such as formed by walls 19, 80. Heat shield 18 extends above emitter surface 16 a distance suilcient to give the resultant electron beam a slightly focused quality.

Conducting rod 14 has its lower end terminated having the shape of a 7 o! the cone being positioned by a dimple in heat shield wall 88. As a point contact only is thus made between rod 14 and end wall 88, very little heat transfer is allowed. The other degree of freedom of motion of the heater structure inside of shield 18 is removed by making the upper sharp edge of the frustum 15 t into an annular concave groove 82 near the top of heat shield 18 and of substantially arcuate cross-section. Such construction results in aline contact, thus very small heat exchange is allowed between the frustum and heat shield 18. One end of heater coil 11 may be spot welded to heat shield 18, as at 84, while the other end is insulated from heat shield 84 by passing out through holes in walls 19, 88. Leads 83 attached to shield 18 pass through the glass press of the vacuum envelope of the tube and provide a rigid support for the cathode structure, and, together with lead 85, supply necessary heater voltages.

It may be desirable to use a larger wattage heater coil in place of coil 11 of Fig. 8 inv which case the structure of Fig. l may be used. The conducting member 14 is now extended Vwell past flange 68 and is of diameter more nearly that of the inner diameter of heat shield 18.. As it passes beyond flange 68, heat shield 18' is enlarged to fit a cylinder 86 which may also be of nickel and which is closed at its lower end by end wall 88. The portion of conductor 14 covered with A1203 and heater coil 89 may be equal-in diameter to the remainder of rod 14, or may be of somewhat greater diameter, as desired, allowing coil 89 to be more easily assembled and to be of greater power capacity. It is to be understood that heater coils 11 and 89 may be of the coiled coil variety if desired, or may be any type of non-inductive winding.

If irustum 15 and heat shield 18 are both of nickel, welding may result due to the usual high operating temperature of such a cathode at the line contact between frustum 15 and annular groove 82, resulting in increased heat transfer between the cathode and heat shield. The structure of Fig. 11 may desired result. The larger diameter of the frustum 15 is made smaller than the inner diameter of h eat shield 18 so that three wires 98, 98', 98" of molybdenum or other suitable material may be inserted between the frustum and the heat shield inner diameter. The wires 98, 98', 98" may be held in position by pressure only or may be bent into slots cut into the upper face of heat shield 18, as at 9|, 9|', 9|," the material of the heat shield adjacent to the slots then being staked to firmly hold wires 98, 98', 98" in proper placement. The heater asse bly may be held in position by a slight tension on lead wires 85, 85', of heater coil 89.

For much shorter output wavelengths, modiiication of the shape of the resonator may be useful in providing sufficient space for cathode and the reector electrode, as is shown in Fig. 12,. This structure is also the invention of Sigurd F. Varian and is claimed in his above-mentioned sole application. Here resonator 92 is made by turning out of a round conducting disk a cavity frustum of a right circular cone provided with an outer wall 93 and an upper apertured wall 94 which carries exit grid 95 of the resonator 92, i. e. where such grid is used. A flexible conducting diaphragm 98 and reentrant apertured portion 91, which is also the frustum of a right circular cone, form the remainder of the resonator boundary. Reentrant portion 91 in a cone 8|. the apex be used to remedy this uncarries entrance grid 98, when used, placed concentric with and close to exit grid 95.

Grids 95 and 98 may, as shown in Fig. 13, consist of radial conducting long and short wires 499 and |88. These grid wires may be inserted in wall 94 and reentrant member 91 by milling radial slots in the upper surfaces of 94 and 91, placing the grid wires in the slots in the correct positio\ns, and exerting hydraulic pressure to those faces great enough to cause the surface metal to ow over the wires, thus staking them in position, or by any other method which will leave relatively smooth surfaces after the grids are inserted.

Outside of the resonator, reentrant portion 91 may be extended as a tube |8| and provided with flange |82`to cooperate with ange |83 attached to resonator body 93, said flanges being used with any desired mechanical tuning mechanism, such as that of Fig. 1. The cathode emitter surface `|84 is placed close to entrance grid 98, and well inside of tube |8|. Cathode |84 may be similar to that shown in Figs. 9 to 11 or of the type shown in Fig. 14 yet to be described, and may be surrounded by a tubular focusing shield |85, which extends past emitter |84 toward grid 98, and which may be supplied with a voltage relative to cathode |88 suilicient to give slight convergence to the resultant electron beam. Focusing shield |85 is supported and supplied with proper voltage by leads |86, which pass through glass press |81. Reector plate |88 is shown as a at disk with a short cylindrical Wall or ange Y assembly is held rigidly by 4at any given cross-section in order projecting toward exit grid 95 from the periphery of said disk. 4

Coupled with resonator 92 by coupling loop |89 is a coaxial line through which ultra high frequency energy may be removed, consisting of small diameter portion ||8, tapered portion lll, and larger diameter portion ||2 containing a glass seal ||3 to provide continuity of the vacnum envelope. same inner-and outer conductor diameter ratios to avoid impedance lumps in the line. rTapered section is provided so that portion I|8 may be of small enough diameter to t the small resonator 92 used. It is evident that any desired number of such coupling loops 'and concentric line posts Vmay be provided with any of the structures herein shown.

The modied form of cathode shown in Fig. 14 is adapted for use in structures such as that shown in Fig. 12, which is also Sigurd F. Varians invention and is claimed in his above-mentioned sole application. This cathode consists of a metal twbe ||4 which acts as a heat shield, projecting past emitter surface ||5 to aord a slight focusing of the electron beam thereby produced, and containing heater coil H6. Emitter surface |15 is made very thin compared to the thickness of tube ||4, and may be oxide coated. The cathode a truss system of wires Il?! arranged in V-formations and supported upon the outer conductor ||8 of a coaxial line celerating voltage being applied between ||8 and |8|. In low frequency circuit theory it is known that circuits may be made broadly resonant by the introduction of resistive losses into the cir- All three of the sections have the resonance curve is spoken of ultra. high frequency devices of the type herein discussed, the introduction of such losses and the consequent broadening of the resonance curve also has certain applications. As has been shown the type shown in Fig. 8 over a considerable frequency range by varying the reilector electrode potential. If means are introduced to broaden the resonance curve of the hollow resonator used, variation of the reflector potential increases the rangeover which the device may have a useful output. Referring to Fig. 15, curve |2| depicts the relation between high frequency output and reflector plate voltage, and curve 22 shows the output frequency as a function of reflector plate voltage. As is seen from the curves, when the slope of curve |22 is increased, due to broadening of the resonance curve, the useful at top portion |23 of curve |2| as yincluded between the dotted lines, corresponds to a larger and larger useful frequency range. In customary terminology, the broadness of a in terms of Q, which is the ratio of energy stored in the circuit per half-cycle to energy lost per half-cycle in ohmic and radiation or other load losses. Reduction of Q means an increase in loss and a consequent broadening of the resonance curve. Resonators such as 9 of Figs. 1 and 8 or 92 of Fig. l2 may be made of iron or other ferromagnetic material or may have their surfaces roughened or coated with a thin lm of a semi-conducting material such as graphite in order to reduce their Q.

Fig. 16 shows a cross-section plan view of a resonator with means for varying Q over a predetermined range as desired. Cylindrical plug |2| may be of graphite or other suitable semiconductor of optimum resistivity and may be projected more or less into resonator |22 by rotation of knob |23' and consequent radial movement of screw |24 which is threaded into end plate |25. Plate |25 closes the outer opening of tube |26, whose inner end terminates at resonator |22'. Glass envelope |21 is provided to prevent leakage around screw |24. As seen, antenna coupling loop |28 is perpendicular to the plane of the figure.

For shorter wavelength resonators, such as that of Fig. 12, the construction shown in Figs. 17 and 18 may be used. This is the sole invention of Arthur E. Harrison and is described and claimed in his copending application entitled, "High-frequency tube structure filed on December 14, 1946. 'Ihe round fiexible diaphragm 96 is now extended nearly to the periphery of resonator body 93. Two metal portions |29, |29' are inserted oppositely against walls 93 and 94, leaving a small space free above flexible diaphragm 96 to allow motion of the diaphragm. The resultant elimination of complete axialsymmetry in the resonator produces a corresponding reduction in Q. It is to :be understood that the structure shown in Figs. 17 and 18 may be greatly varied, and that these figures are intended only to be illustrative of the present invention.

A modified reflector electrode is shown in Fig. 17. This is also the invention of A'rthur E. Harrison, claimed in his above-mentioned copending sole application. It consists of disk |30 operated at or near the potential of cathode |05, and

05 so that a lesser portion of the returning electrons strike wall 04.

Another device for decreasing the Q of a resonator is shown in resonator |34 of Fig. 19. Stretched parallel to flexible diaphragm |32 are a plurality of wires |33, being fastened at one of their ends to tubular conducting wall |35 and at their other ends to the tubular reentrant porance, the geometry of the resonator, and the placement of the wires therein.

It is found that for reflex devices of the above type, and especially for shorter wavelength tubes, it 'becomes desirable to maintain grids |36', |31 always parallel so that the associated cathode and reflector electrode structures remain 1n alignment, as shown in Fig. 19 which is the invention of Sigurd F. Varia and is claimed in his abovementioned copending sole application. Wall |35 and tube |36 of the resonator are considerably extended, and a second flexible diaphragm |38 is used to close the open end of tube |35. Pressure exerted by a tuning lever 43 of a mechanical tuning mechanism which may be similar to that of Fig. 1 forces tube |35 to always move parallel to tube |36, thus maintaining grids |36' and |31 parallel. This method of construction is seen to eliminate some of the complexity of the tuning device, and is seen to also be useful with two resonator electron beam velocity modulating devices.

To obtain perfect alignment of grids |36', |31, cathode |39, and reflector electrode |40, it may be desirable to provide adjustment means for positioning the cathode and reflector. Resonator |34 has its upper wall |48 extended to form ange |4|. Mounted above wall |48 is tube |42 which carries in its open end apertured flexible diaphragm |43. Mounted in the central aperture of diaphragm |43 is tube |44 which is sealed to glass insulator |45 which supports conductor |49 on which reflector electrode |40 is mounted. Tube |44 also carries flange |46, parallel to and spaced from flange |4|. Three screws |41 are mounted at intervals to rotate freely in holes near the periphery of upper flange |46. 'I'he other ends of screws |41 are threaded into flange 4|, and thereby aiord means of adjustment to secure parallelism between exit grid |31 and reflector |40 and the proper spacing of these elements.

Cathode |39, which is mounted on concentric line |50 which projects through glass insulator |5| in the manner described in connection with Fig. 14, and which extends up into the reentrant tube |36, may be similarly adjusted by the action of three spaced screws |52 cooperating with flanges |53 and |54 to cause motion of flexible diaphragm |55.

It may be desired to provide the flexible diaphragm means |43, |55 for preliminary adjustment of cathode and reflector spacings a1; the factory, also providing means to prevent possibility of misalignment at a future date. As seen in Fig. 20 (which is also the invention of Sigurd F. Varian claimed in his above-mentioned copending sole application) in an illustration showing the method as used only on the reflector end of the tube, flanges 4| and |46 and cooperating screws |41 of Fig. 19 are dispensed with. Tube |42 is made to extend well above flexible diaphragm |43, as at |51.

flector plate |43 and grid melting alloy |56 may be After alignment of re- |31 solder or other low poured into the volume the thermal device here and |53, and thus dairied by tube |51, diaphragm |43, and tube |44. After the alloy cools, the jig or other clamping device used in determining the optimum position of the reflector plate may be removed, the alloy thus securing the position of reflector |40. A similar procedure may be used in permanently positioning cathode |39 of Fig. 19.

In the structure of Fig. 19, or in other similar devices using external resonant members cooperating with an electron beam, the mechanical lever 43 may be replaced by the device shown in Fig. 24. Rough adjustment screw 2|5 is shown threaded through thermal insulating bushings 2 1 in bracket 2|6 attached to resonator wall |35, and is held in place by nuts 2I8 and 2|9 threaded thereon. Similarly, screw 220 is mounted in insulating bushings 22| in ilange |53, being locked in place by nuts 222 and 223. Screws 2|5 and 220, facing oppositely, are joined by thin-walled tube 224, which may be coated on its outside with a layer 225 of A1203, and wound with resistance heater' wire 22B, which may be supplied with a variable amount of current from battery 221 and rheostat 228. Heat radiation may be used to heat tube 224, instead of conduction through A1203 layer 225, as by supporting heater wire 226 inside of thin-walled tube 224 if desired. It will be apparent that many other devices, directly electrically controllable, may be used in place of shown to produce predictthe spacing between anges 2|6 to produce changes in the natural frequency of an associated hollow resonator, such as magnetostrictive or piezoelectric or other well known means.

Another form of the thermal tuning device is shown in Fig. 25. Thin-walled tube 240 is attached at right angles to flange 2|6 at 24| and extends through an aperture in flange |53, ending in internally threaded portion 242. Screw 243 which ts into the internal thread 242, acts as a rough adjustment device, and is free to rotate only in end plate 244. End plate 244 closes the outer end of the tube 245, which is concentric to and surrounds thin-walled tube 240. Tube 245 is fastened to flange |53, and extends through ange |53 to almost touch flange 2|6. Thinwalled tube 240 contains a loop of resistance heater wire 245, to the terminals of which may be applied the adjustable controlling voltage. With heat being applied to it from wire 246, thin-walled tube expands or contracts with a minimum of time delay due to its thinness and large radiation surface. Tube 245 is preferably of Invar or other low and acts to shield tube 240 from sudden temperature changes due to drafts. The subject matter of Figs. 24 and 25 is the joint invention of John R. Woodyard and Sigurd F. Varian and is claimed in their copendingl application, Serial No. 513,090, led December 6, 1943.

Another arrangement motion of the resonator tube is shown in Fig. 21. The tube may be simllar to that shown in Fig. 1 and consists of end bell |58 containing the cathode structure, resonator |59, tube |60 containing the reector electrode supported by glass end bell |6|. Facing and soldered to end wall able changes in that provides parallel grids of the reilex type its cylindrical sides, elongated holes |66 whose thermal expansion coecient metal,

|62 of cathode end |58;` is an apertured disk |63, which has an internally 12 major axes are parallel to the axis of the tube. The upper end of the casting |65 has an apertured top portion |61 containing apertured bushing |68 which is internally threaded.

Tube |60 has attached concentric to it threaded flange |10 which supports a, cylindrical casting |1| with top portion |12 integrally attached. Casting |1| may have elongated holes |13 similar to those of casting |65, and top |12 contains a centrally located apertured bushing |14 which is also internally threaded. Bushing |68 projects through a hole in a panel |15, on which' the device may be mounted, said bushing being of diminished diameter where it extends through panel |15 and being supplied with lock nuts |16 and |11 on the side of panel |15 opposite to the reflex tube.

Projecting through bushing |68 is a threaded shaft |18 which mounts. knob |19 having index marks |80 cooperating with index marks on concentric tube |8| also held xed to panel |15 by nuts |16 and |11. Threaded portion |82 of shaft |18 screws into bushing |68, shaft |18 being further extended toward the reiiex tube as a smaller threaded portion |83, which, in turn, threads into bushing |14 of casting top |12. Shaft portion'IZ is provided with a right-hand thread of one pitch,

and shaft portion |83 with a left-hand of lesser pitch, so that a differential screw is provided, whereby rotation of knob |19 causes a very small change in the distance between bushings |68 and |14, consequently causing an equally very small change in the distance between the resonator grids. It is seen that air may be forced in through holes |66 and |13 on one side of the tuner by a suitable blower, around the electron tube, thereby cooling it, and out through holes |13, |65 on the opposite side of the tuner, if desired. This structure is the invention of Edward L. Ginzton and is claimed in his above-mentioned copending sole application.

As disclosed in United States Letters Patent No. 2,280,824, the resonator of an electron beam velocity modulation A,tube may be applied externally to the vacuum envelope. Figs. 22 and 23 illustrate an improvement in such a device. Resonator |82 is coupled by capacitative concentric tubes |83 and |84, which may be of nickel, to exit grid |85, which may be of copper, through vacuum envelope |89, which may be of quartz or low loss glass; and is also seen to be coupled by capacitative concentric tubes |86 and |81 through vacuum envelope |89 to entrance grid |88. Vacuum envelope |89 supports cathode |90 near entrance grid |88 and reiiector electrode |9| near exit grid |85. Cathode |90 is supported by insulator |9|' and leads |92 which pass through glass press |93. Tubes |84 and |81 are positioned and grounded or held at desired potential by leads 230, 23 respectively.

Serious loss of energy which may result by leakage of energy out through the vacuum envelope from between the capacitative elements coupling the resonator and grids is prevented in the present construction. Tubular wall |96 of resonator |82 is extended in both directions, to form the outer wall of cavities |91, |98 on each side thereof. The ends of cavities |91, |98 are closed by apertured round end plates |99, 200, respectively, tubes 20|, 202, which just slide over the outer diameter of vacuum envelope |89, being fastened to apertured disks |99, 200, respectively, so'that a portion of each tube 20|, 202 extends into cavities |91, |98 and a portion extends on past disks |99, 200, respectively. Inner capacitative eletube 202, the impedance seen looking from point 204 toward point 203 is I 86 are of equal cross` the section of line de- |06 may also be called Z1. Then at point 206 is seen to be:

2.2.2.2 22212' or 222B In general, the lter structure shown in Fig. 9 may be designed so that this impedance may be If desired,

The concentric line 2| bearing coupling loop 2| 2 is shown insulated from wall 96 of resonator |82 by means of insulating bushing 2|3, so that, if desired, resonator |82 may be held at any desired potential relative to coaxial line 2| I. Tuning of resonator |82 may be accomplished by rotation of screw 2H, as disclosed in the aforementioned Patent No. 2,259,690. Similar screws or other tuning means may be provided in semi-resonant cavities |91, |98, if desirable.

As many changes could 'be made in the above construction'and many apparently widely diierent embodiments of frequency control means connected to and operated by said movable means for tuning said resonator, whereby a unitary tuning and mounting mechanism is provide 2. A tuning and support mechanism for tuning for varying the spacing between said walls to provide tuning of said resonator.

4. Frequency control apparatus comprising a hollow resonator device having two relatively between said lever and the other part.

5. Frequency control apparatus comprising a hollow resonator device having two relatively movable frequency-determining parts mounted in spaced relation longitudinally of said device,

said bracket.

7. Frequency control apparatus comprising a hollow resonator device having two relatively movable frequency-determining parts mounted in 8. 'I'he frequency control claim 7, wherein said relatively movable parts are for projecting a stream of electrons through said resonator, frequency control means operably connected to said resonator comprising two relatively movable members, and means for effecting relative movement of said members comprising a bent lever pivotally connected to one of said members, a strut extending between said lever and the other of said members substantially parallel to said electron stream, and a control member operatively coupled to said lever and movable in a direction angularly disposed with respect to said stream.

10. Frequency control apparatus for a hollow resonator device having frequency-adjusting means comprising a rigid bracket having a first arm adapted to be fixed to said device and a second arm extending at an angle with respect to said first arm, a control member adjustably mounted on said second arm and adapted to `coact with said frequency-adjusting means, and means coupled to said member for measurably adjusting said control member.

11. The control apparatus defined in claim 10, wherein said means for adjusting said control member comprises a micrometer screw assembly.

12. The control apparatus dened in claim 10, including means on said second arm for attaching said bracket to a supporting panel or the like.

13. Frequency control apparatus for a hollow resonator device comprising a substantially L.- shaped bracket, means on an arm of said bracket for fixing said bracket to said device, an axially adjustable member mounted on the other arm of said bracket, and a micrometer assembly supported on said other .arm and operativelyconnected to said member for measurably adjusting said member.

14. Frequency control apparatus comprising a hollow resonator device provided with spaced electron-permeable walls. radially extending flanges on said device rigid with the respective walls, springs interconnecting said flanges, a lever pivoted on one of said flanges, strut means between the lever and the other of said flanges, a bracket rigid with said one ange, and means on said bracket adjustable for moving said lever about its pivot.

15. Electron discharge apparatus comprising a base structure, a hollow resonator mounted on said base structure and provided with aligned adjustably interconnected s electronipermeable walls, one of said walls beingrigidly secured to said base structure, cathode means in said base structure for projecting a stream of electrons through said walls to couple said stream with the resonator, an electron-reflecting electrode mounted in said apparatus beyond said resonator for returning electrons of said stream ,into said resonator, and adjustable strut means interconnecting said base structure and that part of said resonator which is rigid with the other of said walls for varying the spacing between said walls for tuning said resonator.

16. Electron discharge apparatus comprising a Ibase structure, a hollow resonator mounted on said basestructure and provided with aligned adiustably interconnected electron-permeable walls, means rigidly securing said base structure to one of said walls, cathode means in said base structure for projecting a stream of electrons4 through `said walls torcouple said stream with said resonator. an electron-reflecting electrode mounted in said apparatus beyond said resonator for returning electrons of said stream into said resonator, and spring-biased adjustable strut means interconnecting said base structure and that part of said resonator which is rigid with the other of said walls for varying the spacing between said walls.

17. Electron discharge apparatus comprising a hollow resonator body having an end. wall rigid with said body and formed with a rst electronpermeable wall portion, a flex-ible wall at the other end of said body, a hollow pole carried by said exible wall and projecting into said resonator and having an electron-permeable end portion adjacent to and aligned with said rst wall portion, a base secured to said pole, a reector electrode mounted on said resonator body in alignment with said wall portions, a cathode carried by said base for projecting a stream of electrons through said wall portions toward said reflector, and means operably interconnected between said base and said resonator body for varying the spacing between said wall portions.

18. The electron discharge apparatus defined in claim 1'7, wherein said last means includes a bracket secured to said base, pivoted lever and strut means interposed between said base and resonator body, and means on said bracket for ad justing said lever and strut means.

19.` High frequency electron discharge tube structure comprising means dening a hollow resonator having opposed walls formed with aligned electron-permeable sections, a base structure rigid with one of said sections, an electron reector electrode aligned with said sections and rigid with the other of said sections, and frequency control means operably interconnected between said base structure and that portion of said resonator rigid with said other section and providing relative adjustment between said one section on the one hand and said reector and said other section on the other hand.

20. The high frequency tube structure dened in claim 19, wherein one of said walls is formed with a reentrant part having an electron-permeable section near the electron-permeable section in the other wall, and wherein one of the resonator walls is formed with a fiexible portion enabling said adjustment.

21. High frequency tube structure comprising a resonator body having exibly connected opposed spaced electron-permeable wall portions, a base structure rigid with one of said wall portions, means supported by said base structure for projecting an electron beam through said wall portions, frequency control means operably connected between said base structure and that portion of said resonator body which is rigid with the other of said wall portions for varying the spacing of said wall portions and hence the frequency of said resonator, insulator support means rigid with said resonator body, and a reector electrode mounted on said support means for returning said beam into said resonator.

22. High frequency tube structure comprising a rigid cup-shaped resonator body member, a exible wall closing the end of said body member, said body member and wall being apertured in alignment, a base structure, means aligned with said apertured member and wall and carried by said base structure for projecting an electron beam through the apertures of said apertured member and apertured wall, a reflector electrode located along the path of said beam for returning said beam into said resonator, insulation support means rigid with said resonator body member mounting said reflector electrode, and adjustable means connected between said resonator raperture in said other body member and said base structure for varying the frequency of said resonator. l

23. High frequency tube structure comprising a hollow resonator having a exible wall portion and a rigid end wall portion, said wall portions having substantially aligned apertures, means oscillatory field lWithin said resonator, and a tubular high frequency transmission line extending substantially parallel to the path of said electron stream and having an end secured in an aperture in said rigid wail portion.

2d. Electron discharge apparatus comprising a hollow resonator body having an apertured end wall rigid with said body,y an apertured exible wall at the other end of said body, a hollow pole carried by one of said Walls and projecting into said resonator and having an electron-permeable end portion adjacent to and aligned with the wall,y a base structure secured to said pole, a reector electrode mounted on said resonator body inf alignment with said CII said resonator, means nxedly interconnecting said reector electrode with said rigid Wall portion, and tuning .means connected 'to said wall portions for controlling the spaeing oi said apertures.

ARTHUR E., HARRISON. SIGURU R VARIAN. 

